Zihua Guo

Tsinghua University, Peping, Beijing, China

Are you Zihua Guo?

Claim your profile

Publications (40)27.47 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, in-sequence delivery delay of an acknowledged mode radio link control (AM-RLC) protocol in wideband code division multiple access (W-CDMA) networks is studied. Two special protocol phenomena, duplicated retransmission, and delayed acknowledgment, are reported. A two-step dependent Markov chain is adopted to model the AM-RLC protocol. The in-sequence delivery is evaluated by means of an analysis through tracking the transmission status of a specific packet data unit (PDU) and its blocking PDUs. Analysis results indicate that in-sequence delivery delay is approximately linear with frame error rate. Analysis results also exhibit that in-sequence delivery delay is highly related to status report interval. Based on this observation, a dynamic AM-RLC scheme is proposed. The proposed AM-RLC scheme dynamically changes status report interval according to channel status. Extensive simulations are carried out to verify the effectiveness of the proposed scheme. It is found that the proposed scheme can reduce status report without penalty to in-sequence delivery delay.
    Wireless Personal Communications 11/2007; 43(4):1209-1227. · 0.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ultra wideband (UWB) network brings both chance and challenge to personal area wireless communications. Compared with other IEEE 802 small range wireless protocols (such as WLAN and Bluetooth), UWB has both extremely high bandwidth (up to 480 Mbps) and low radiation. Moreover, the structured MAC layer of UWB is the fundamental difference to WLAN. The top one is that only when two UWB devices belong to the same piconet can they communicate with each other directly, which means that we must jointly consider topology formation and routing when deploying UWB networks because the interaction between routing and topology formation makes separate optimization ineffective. This paper tries to optimize UWB network from a cross-layer point of view. Specifically, given device spatial distribution and traffic requirement, we want to form piconets and determine routing jointly, to maximize the overall throughput. We formulate the problem of joint optimization to mixed-integer programming and give a practical lower bound that is very close to the theoretical upper bound in our simulation. Furthermore, our lower bound is much better than an algorithm that only considers topology formation in UWB networks.
    Science in China Series F Information Sciences 01/2007; 50(5):760-770. · 0.66 Impact Factor
  • Min Li, Zihua Guo, R.Y. Yao, Wenwu Zhu
    [Show abstract] [Hide abstract]
    ABSTRACT: Multimedia decoding is one of the key parts of many popular mobile multimedia applications, such as video telephony, streaming, and video playback. Since the multimedia decoding consumes a significant amount of energy on processors, it is crucial to lower the power consumption and prolong the battery life. In this paper, the statistical analysis of more than 600 processor load trace files is first presented. From the analysis, we found that it is feasible to predict the processor load of multimedia applications accurately using a low order linear time series model if the load is sampled using the feature period, which is obtained with fast Fourier transformation. Based on the analysis, we propose a novel interval-based DVS scheme to achieve penalty controllable energy reduction. The DVS scheme does not need any task profile or involvement of application program, and it is compatible with the service model of general purpose mobile operating systems. In addition, the proposed DVS scheme can handle the nonstationary behavior using an efficient online change detector, and important parameters, such as coefficients of the linear time series model, are estimated on the fly. More importantly, the proposed scheme can keep the overscaling rate (OSR) around a certain predefined value. Since the OSR has a simple and stable relationship with the deadline miss rate (DMR), the penalty incurred by DVS is effectively controlled. Experimental results show that the proposed DVS scheme achieves a much smaller prediction error than previous approaches and achieves a significant processor energy reduction with adjustable and controlled penalty
    IEEE Transactions on Mobile Computing 01/2007; 5(12):1719-1733. · 2.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To provide a reliable transmission in 3GPP WCDMA systems, in the Radio Link Control (RLC) sublayer of the WCDMA, an Acknowledgement Mode (AM) is defined where an ACK frame is sent to indicate the data frame receiving status. In order to design a well-performed AM scheme, in this paper, we first investigate the AM protocol behavior and present the delay performance of the standard periodical AM-RLC scheme in the Bernoulli channel. Then, based on the observation from the performance above, we propose a dynamic AM scheme in RLC over a more general time-varying Markov channel. It is demonstrated that a much better delay performance can be achieved compared with the standard AM scheme with periodical acknowledgements.
    Communications, 2006. ICC '06. IEEE International Conference on; 07/2006
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper addresses the throughput optimization problem in multihop ultra-wideband (UWB) networks by jointly considering network topology formation and routing. Given a spatial distribution of UWB devices and traffic requirement, we want to form piconets and select paths to maximize the network throughput. Although there have been several works considering the problem of selecting paths to achieve the optimal throughput in multihop wireless networks, to the best of our knowledge, none of them takes the topology formation into the consideration. In this paper, we use Boolean matrices to model role assignment in UWB networks and formulate the throughput optimization problem as a nonlinear programming (NLP) problem. Since the throughput optimization problem is NP-hard, we give an upper bound of the optimal throughput by relaxing some constraints and using pseudo-Boolean optimization to linearize the NLP. We prove that the solution of the upper bound is at most three times of the optimal throughput. Based on the topology formed by solving the upper bound, we formulate a lower bound of the optimal throughput as a linear programming problem and use column generation to solve the lower bound. Numerical results show that the lower bound is very close to the upper bound. Simulation results demonstrate the effectiveness of the scheme.
    IEEE Journal on Selected Areas in Communications 05/2006; · 3.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The wireless personal area network (WPAN) is designed for short-range connectivity among fixed or portable moving devices. The ultra-wideband (UWB) technology is being defined as the physical-layer (PHY) support for the high-rate WPAN. At medium access control (MAC) layer of the WPAN, a delayed acknowledgment (Dly-ACK) or burst-ACK (B-ACK) scheme is introduced to improve the channel utilization by reducing the overhead of ACK. In this paper, the authors first study the delay performance of the Dly-ACK scheme. An analytical model is developed for the Dly-ACK mechanism, and the delay is decomposed into queuing delay and delivery delay. These delay metrics are derived, and some important observations are obtained. In particular, there exists an optimal burst size, which is determined by the input traffic load and is very insensitive to the channel error rate within a normal error-rate range. It is also demonstrated that Dly-ACK cannot work properly if the burst size is fixed. The authors then propose a dynamical Dly-ACK scheme that can adaptively change its burst size according to the queue buffer size. Simulation results show that the dynamical scheme can improve the delay performance significantly.
    IEEE Transactions on Vehicular Technology 04/2006; · 2.06 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Beacon period (BP) is an overhead in UWB MBOA MAC, since no data frame is allowed during a BP. In this letter, we model the current BP contraction scheme in MBOA spec as a greedy distance-2 graph coloring algorithm, and formulate the BP contraction problem as a 0-1 programming problem. The theoretical numerical results show that the current BP contraction algorithm has good performance. Furthermore, we study the impact of device joining/leaving order on the performance of the algorithm. Simulation results demonstrate that the impact is not significant and the performance of the algorithm is stable with varied device ordering. Therefore, we conclude that there is no much room for any further significant improvement over the current BP contraction algorithm in MBOA spec.
    IEEE Communications Letters 11/2005; · 1.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The software codec on mobile device introduces significant power consumption because the energy efficiency of general processor based system is much lower than that of the dedicated hardware such as ASIC based accelerator. Dynamical voltage scaling (DVS) is one of the most efficient techniques to promote the energy efficiency. Most existing papers on this topic use simple heuristics to predict processor load, and poor prediction accuracy is observed in experiments. We advocate intensive analysis on processor load before designing DVS framework and algorithm. Hence, we conduct load analysis on more than 600 processor load trace files for 57 test sequences and 98 representative clips from Internet. Basic statistical analysis and time series analysis are applied intensively to identify major characteristics of the processor load. The analysis shows that it is feasible to predict processor load using low order linear time series model if the load is sampled using feature period. Moreover, there is indeed significant potential to reduce the energy consumption. Based on the analysis results, we develop a fully adaptive DVS technique to adjust supply voltage online with controllable penalty
    Multimedia and Expo, 2005. ICME 2005. IEEE International Conference on; 08/2005
  • Zhihua Tao, Zihua Guo, R. Yao
    [Show abstract] [Hide abstract]
    ABSTRACT: IEEE 802.15.3 is designed for short-distance wireless connectivity within a wireless personal area network (WPAN). It has great significance for applications such as home networking. Security is one of the fundamental issues in IEEE 802.15.3 WPAN. Although several security mechanisms have been defined in the standard, there are many others open and left for implementation. Therefore, in this paper, by utilizing the unique characteristics of the IEEE 802.15.3 WPAN, we propose a certificate-based trust management (including device initialization and certificate management) and key establishment scheme to protect the IEEE 802.15.3 WPAN.
    Wireless Communications and Networking Conference, 2005 IEEE; 04/2005
  • [Show abstract] [Hide abstract]
    ABSTRACT: Power management (PM) is critical for the portable devices in IEEE 802.15.3 wireless personal area networks (WPAN). Due to the property of TDMA based MAC of 802.15.3, one of the key issues for PM is to schedule the order of the multiple streams among multiple users to minimize the total wakeup times. In this paper, we reveal that this PM problem is in general a Hamilton path problem. With the aid of graph theory, we derive the lower bound and upper bound for the minimum wakeup times. Then, an efficient MDS (min-degree searching) algorithm is proposed to find the suboptimal order. The simulation results show that the MDS algorithm is usually near-optimal and can actually achieve the lower bound in most cases and performs much better than the existing approach.
    IEEE Communications Letters 04/2005; · 1.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The life of battery power available time is a crucial character of the battery powered mobile device. In this paper, we investigate the performance issues of upper layer protocol, such as TCP, in IEEE 802.11 LAN's power saving mode. We discuss the tradeoff of energy saving, networking throughput and response time at the points of user experience. A novel power efficiency scheme is proposed to control the traffic transmission in power saving mode, which takes the QoS requirements of applications into account. Finally, we show that the proposed schema achieves higher user experience in our experiment.
    Consumer Communications and Networking Conference, 2005. CCNC. 2005 Second IEEE; 02/2005
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dly-ACK scheme in IEEE 802.15.3 MAC is designed to reduce the overhead of the ACK frame in MAC layer and improve the channel utilization. However, how to using the Dly-ACK is open for implementation. In this paper, we propose an adaptive Dly-ACK scheme for both TCP and UDP traffic. We first point out the problems of applying fixed Dly-ACK scheme to these two traffic scenarios and show that the system performance is rather poor and the causes of these problems are presented. Based on our observations, two enhancement mechanisms for fixed Dly-ACK are then proposed. The first one is to request the Dly-ACK frame adaptively or change the burst size of Dly-ACK according to the transmitter queue status. The second is a retransmission counter to enable the destination DEV to deliver the MAC data frames to upper layer timely and orderly. Simulation results show that, with our enhancements, the system performance can be improved significantly compared with the conventional Imm-ACK and fixed Dly-ACK. We also investigate the impacts of some important parameters such as the buffer size on the system performance. Some important guidelines for the Dly-ACK design are given. Finally, it is worth to point out that our Dly-ACK enhancements are compatible with the standard and it is transparent to the upper layer protocols, i.e., either UDP or TCP.
    IEICE Transactions. 01/2005; 88-A:2364-2372.
  • IEEE Communications Letters. 01/2005; 9:228-230.
  • Zhenqi Chen, R. Yao, Zihua Guo
    [Show abstract] [Hide abstract]
    ABSTRACT: The electromagnetic transmission phenomenon is one of the most important parts of propagation modeling of UWB signals in the indoor environment. However, in previous work there has not been an efficient solution for the transmission of UWB signals. In this paper, we develop an analytical time-domain solution of a transmitted electric field through a lossy dielectric slab excited by an oblique incident plane wave. This solution is derived from the inverse Laplace transform of refraction coefficients at both surfaces of the slab and propagation losses in the slab. Based on the solution, a detailed investigation is presented on the transmitted field waveform for UWB signals passing through lossy dielectric slabs in varied scenarios of an indoor environment. Finally, we discuss the transmission loss of different slabs in the indoor environment and how to efficiently apply our solution efficiently in modeling the UWB propagation.
    Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
  • Yu Cai, Zihua Guo, R. Yao
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we introduce a novel design for the medium access control (MAC) layer of IEEE 802.15.3, which is defined for a high-rate WPAN system. We split the 802.15.3 MAC into two layers: upper layer MAC and lower layer MAC, according to the different timing requirements. Thus, our MAC implementation includes two main modules: (1) a 802.15.3 network interface card (NIC) which is responsible for only direct transmission/reception and other timing critical functions such as protocol accelerator; (2) a driver in operating system (OS) which is a flexible plug-in module and allows us to implement some non-timing-critical intelligent algorithms. The proposed approach has many advantages such as scalability, flexibility and low cost for chip vendors.
    Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper addresses the problem of energy efficient transmission in an IEEE 802.15.3 WPAN based on UWB technology. We consider devices with heterogeneous energy attributes. That is, some of the devices are battery-powered and energy sensitive, while others may have more power, or even AC powered. Our objective is to design an energy efficient transmission protocol to optimize the energy efficiency of the energy sensitive devices. That is, to minimize the energy consumption per bit. To achieve this, we utilize the network topology and UWB physical layer information in an energy-aware system design framework. Specifically, we propose a novel scheme to exploit the following key ideas: (1) efficient TDMA MAC for sleep/wakeup switch and network information exchange, (2) dual communication mode considering different transmission paths, namely, peer to peer and relay, and (3) UWB PHY characteristics (multi-rate and precise location information). The simulation results have verified the effectiveness of the proposed scheme in various scenarios.
    Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
  • Weiyu Xu, Zhenqi Chen, Zihua Guo, R. Yao
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a novel reduced-complexity maximum-likelihood (ML) detector for multi-user impulse radio ultra-wideband (UWB) signals in multi-path channels. By utilizing the unique trellis feature of a multi-user impulse radio UWB signal, and introducing a novel combined stack and Viterbi based trellis search (CSVS) algorithm, the proposed detector is optimal and enjoys much lower computation complexity compared with the brute-force search based ML detector. Simulation results show that the proposed detector achieves much better performance than the conventional simple matched filter UWB detector.
    Radio and Wireless Conference, 2004 IEEE; 10/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: Roaming across heterogeneous wireless networks such as wireless wide area network (WWAN) and wireless local area network (WLAN) poses considerable challenges, as it is usually difficult to maintain the existing connections and guarantee the necessary quality-of-service. This paper proposes a novel seamless and proactive end-to-end mobility management system, which can maintain the connections based on the end-to-end principle by incorporating an intelligent network status detection mechanism. The proposed system consists of two components, connection manager (CM) and virtual connectivity (VC). The CM, by using novel media access control-layer and physical-layer sensing techniques, can obtain accurate network condition, while at the same time reducing the unnecessary handoff and ping-pong effect. The VC can make mobility transparent to applications without additional network-layer infrastructure support using a local connection translation, and can handle mobility well in the network address translator and simultaneous movement cases using a subscription/notification service. The proposed system enjoys several unique advantages: 1) capable of reacting to roaming events proactively and accurately; 2) maintaining the connection's continuity with small handoff delay; and 3) being a unified end-to-end approach for both IPv4 and IPv6 networks. We have built a prototype system and performed experiments to demonstrate the advantages of the proposed system.
    IEEE Journal on Selected Areas in Communications 07/2004; · 3.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In current WLAN system that is designed for best-effort communications, there is not any quality of service (QoS) differentiation support. In this paper, we propose a fully distributed medium access control (MAC) adaptation method for service differentiation. It is implemented by dynamically updating the MAC layer parameters (such as contention window) to adapt to the network conditions in a class-based fashion. In this sense, the QoS classes are differentiated and the system performance is significantly improved in terms of delay, packet loss and throughput while ensuring fairness and stability. The key idea of our scheme is the introduction of a mapping function and a target contention window. It is demonstrated that our proposed adaptive MAC can outperform both the basic 802.11 MAC and the fixed differentiation scheme with very low complexity.
    Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
  • Source
    Zihua Guo, K.B. Letaief
    [Show abstract] [Hide abstract]
    ABSTRACT: The performance of multirate direct-sequence code-division multiple-access (CDMA) systems is considered. We compare two multirate schemes: variable spreading length (VSL-CDMA) and multicode (MC-CDMA). The performance in terms of asymptotic multiuser efficiency (AME) and near-far resistance (NFR) for various detectors are evaluated. Analytical and numerical results demonstrate that in multirate systems, MC-CDMA has a similar performance to that of VSL-CDMA employing low-rate detection in terms of multirate AME (MAME) and multirate NFR (MNFR). A lower bound for the optimal MNFR is also obtained and is shown to be that of the linear decorrelator in multirate systems. Thus, this implies that the decorrelator is no longer optimal in the sense of MNFR.
    IEEE Transactions on Communications 01/2004; · 1.75 Impact Factor